1. Field of the Invention
The present invention generally relates to a dispenser cap and more particularly, to a dispenser cap which is applicable to the mouth of a fluid substance container and operable, by simple rotation to close the container mouth and to open the container mouth to enable the substance to be dispensed.
2. Discussion of Background
Various types of cap are known to be applicable to a container mouth to close or open the passage through the mouth by simply rotating the outermost component forming part of each cap.
U.S. Pat. Nos. 5,004,127 and 5,421,487 (corresponding to EP-B-0598223) describe caps formed from three separate, but mutually cooperating parts. A first part is securely fixed on the container mouth. A second part is rotatable about the first. A third component part is rotatably constrained to the second part, but relative to which the second part, can freely slide axially. The third component part is connected to the first part by a screw coupling or similar in such a manner as to slide axially to the first part when the second part is rotated about the first part.
As will be apparent, the structure of such caps is very complicated and their cost is high. One reason for the high cost is the difficulty of constructing the coupling systems between their constituent parts with the necessary precision.
Caps of simpler structure, formed in only two parts, are described in U.S. Pat. No. 4,690,304. The two pieces are secured together by a cam or screw system such that rotating the first piece causes the second piece to slide relative to it, with consequent opening or closure of the discharge hole in the cap. The structure of this cap is complex and costly and requires the container mouth to be especially shaped to fix and retain one of the two pieces forming the cap.
EP-A-0270134 also describes a cap formed in two pieces, wherein one is screwed onto the other. The inner piece is superposed on and screwed onto a thread provided on the outside of the container neck. The cap structure is complex because a screw coupling system has to be provided between the two constituent pieces of the cap.
The caps described in the above described patents all have a serious drawback deriving from the fact that the two or three constituent parts of the caps are positioned on the outside of the mouth or neck of the container on which they are mounted.
The caps are fairly large in size (in terms of their cross-section), which means that if the container neck is of normal size (ie., having a relatively large cross-section), the cap has necessarily to have an even greater cross-section, which is unacceptable.
This means that to keep the cap cross-section within acceptably small values, the only usable and practical solution (which is that followed in practice) is to considerably reduce the cross-section of the container mouth or neck to much less than the usual transverse dimensions of the mouth or neck of a normal container of equal capacity. This has a further serious consequence, namely that the hole through which the fluid substance (liquid or cream) is fed into the container by automatic machines is small. Hence the container filling operation is slowed, requiring the filling machine to be adjusted differently depending on whether the mouth is to be closed by a normal one-piece closure cap or whether a dispenser cap of known type is to be used on it.
Dispenser caps formed in only two pieces are already described in U.S. Pat. Nos. 3,010,619, 3,240,404 and FR-A-1113774. One of the two pieces is a hollow profiled body. One portion of the hollow profiled body is inserted and retained in the hole of a container neck. A second of the two pieces is a head, superposed on the hollow profiled body and lying above the free end of the container neck. On the outer surface of the neck of the container, a thread with which a thread provided inside the head engages.
The head can be rotated on the threaded container neck to traverse, relative thereto, from a lowered position, in which a discharge hole, provided at the top of the head, is pressed and sealed against the end of an appendix projecting from the body, and a position in which the head discharge hole is raised from the appendix to free the discharge hole, through which the substance contained in the container, on which the cap is mounted, can flow out.
The caps described in the three above-described patents have the serious drawback that their constituent head can be freely unscrewed and removed from the container neck, to leave the body still fitted to the neck, so that the substance contained in the container can be accidentally spilled.
The above-described problem is partially solved by the cap described in FR-A-1370761. This cap is also in two parts such as those described in the three above-described patents, but comprises opposing annular ribs projecting from the profiled body and head. The annular ribs projecting from the profiled body and the head mutually interfere with each other, when the head is unscrewed from the container neck (ie., to free the discharge hole provided in it) thus, hindering or preventing separation of the head from the body. However, there is again a serious drawback, in that if the head is rotated in the unscrewing direction to a greater degree than is necessary to completely open the discharge hole, the annular rib on the head engages the annular rib on the body and drags it axially to extract the body from the hole in the container neck. This occurs because the head can exert a strong dragging action on the body in the axial direction, even though the force necessary to rotate the head around the neck thread is small. The result is that the entire dispenser cap can easily separate from the container neck, and the substance in the container be poured out without any control.